Core barrel latching and sealing method and apparatus



1.. J. MARTINSEN 3,485,308

CORE BARREL LATCHING AND SEALING METHOD AND APPARATUS Filed Jan. 21, 1969 INVENTOR. LYLE J. MARTINSEN BY :34 6 2 FIG. 5 ATTORNEY I l I Uted States Patent 0 No. 792,53a

hit. or. E21b 25/00 US. Cl. 17558 10 Claims ABSTRACT OF THE DISCLOSURE A core barrel assembly adapted for use principally in horizontal or up holes comprising spearhead core barrel outer tube coupling latch structure comprising resilient fingers disposed at the trailing end of the assembly which is provided with novel fluid seal segments selectively preventing bypass of fluid along the core barrel assembly (sometimes called the core barrel inner tube assembly) to accommodate drilling fluid pressure displacement of the core barrel assembly to the leading end of the drill string whereupon the latch structure is secured in an annular coupling recess in the outer tube of the drill string. The fluid seal segments part or separate one from another when the latch structure is coupled to the outer tube thereby providing an axial fluid passageway at the trailing end of the core barrel assembly. Preferably, the seal segments are compressively yieldable to allow the resilient fingers to be gathered by an overshot during core barrel assembly retrieval procedures. The latch structure is also uniquely configurated to provide improved coupling between the latch structure and the outer tube.

This application is a continuation-in-part of my copending US. patent application Ser. No. 571,521, filed Aug. 10, 1966, now Patent No. 3,441,098.

The present invention has to do with a core barrel assembly and related methods and more particularly to an improved method for pressure displacing a core barrel assembly and novel fluid seal structure comprising part of improved spearhead latching-outer tube coupling latch structure in the form of resilient fingers or prongs, which seal structure accommodates hydraulic pressure displacement of the core barrel assembly to the leading end of an outer tube of a drill string. The invention further relates to a novel coupling ridge which securely maintains the core barrel assembly against inadvertent uncoupling from the outer tube.

As used herein drill string means consecutive lengths of joined drill pipe disposed in a hole and core barrel assembly means the combination of the core-receiving inner tube, the swivel mechanism and the latch structure and excludes the outer tube to which the latch structure is coupled during drilling.

It has been a long-standing problem in the core drilling art to efliciently displace a core barrel assembly in a horizontal or in an up hole to its latching position at the leading end of an outer tube to receive the core as it is drilled. Prior art devices, presently extensively used to my knowledge, comprise a plurality of parts, including placement structure, which cooperate and which cause a fluid seal to be formed with the drill string to allow the core barrel assembly to be displaced axially within the outer tube by fluid pressure. The placement tructure, in order to be retrieved after the core barrel assembly has been suitably positioned at the drilling site, must be attached to a wire line (cable). This attachment dramatically curtails the rate at which the placement structure and core barrel assembly can be fluid pressure-displaced in the drill string because the resistance to displacement not 3,485,308 Patented Dec. 23, 1969 only comprises the friction created by the seal of the placement structure, but also includes the additional load or weight of the wire line plus the resistance of the packing gland seal at the pump end of the drill string which squeezes the wire line. Also, when the placement structure is retrieved from an overhead hole, the drill string is drained, with some fluid back-pressure being maintained to prevent wire line tangle; this takes time, as well as requiring additional time to subsequently refill the drill string with drilling fluid.

When drilling in a near horizontal down hole, the seal of the conventional placement structure will swab the hole dry of drilling fluid during retraction of the placement structure. This creates another problem, i.e. contaminated drilling fluid disposed outside the drill pipe adjacent the drill hole is caused to 'flow intothe drill pipe bringing with it much debris. This at least partially clogs the outer tube which, inter alia, significantly increases the danger of a subsequent mis-latch between the latch structure at the trailing end of the core barrel assembly and the outer tube.

Placement structure designed to be used without a wire line has been proposed. These placement structures, which are expensive and complex being comprised of many mechanically-moving parts, are prone to malfunction.

With the foregoing in mind, it is a primary object of the present invention to provide novel methods and apparatus for dependably and efliciently placing a core barrel assembly in its drilling position at the leading end of a drill string.

The mentioned primary object is accomplished by the present invention which includes method and apparatus by novel structure at the trailing end of a core barrel assembly; this novel structure comprises improved trailing resilient fingers. The resilient fingers each provide (1) speakhead latching structure, (2) outer tube coupling structure and (3) sealing structure for establishing a complete fluid seal within the drill string. The outer tube coupling structure of each finger preferably comprises a radial-extending ridge, which tapered divergently radially outward at top and bottom surfaces; the ridge is received in coupling relation by a complementarily-shaped coupling recess in the outer tube. Each finger inwardly presents a seal segment, the seal segments cooperating to prevent fluid flow through the core barrel assembly only when the fingers are slightly gathered, i.e. when the core barrel assembly is disposed within the drill string and out of coupling relation with the coupling recess in the outer tube thereof. The sealing structure, comprising the segments, accommodates displacement of the core-barrel assembly through the drill string to the drilling site under force of drilling fluid pressure, Without need of a wire line or complex placement structure. The present invention has its principal use in generally horizontal and up holes, although the invention also has application in down holes, as, for example, when a positive indication of secure coupling with the recess of the outer tube is desired.

It is also a substantial object of this invention to provide novel methods and apparatus for placing a core barrel assembly in its drilling position by fluid pressure, which methods and apparatus are easy and economical to use which do not malfunction and which consume during placement, only a small fraction of the time consumed by relevant prior art placement methods and apparatus.

It is another primary object of the present invention to provide an improved method and novel structure at the trailing end of a core barrel assembly to accommodate displacement of the bore barrel assembly through the drill string to the drilling site by pressure of the drilling fluid.

. It.isanother importantobject of the present invention to provide novel structure and method accommodating opening and closing of a fluid passageway at the trailing end of a core barrel assembly under predetermined conditions without reliance on mechanically-moving parts.

Itis another dominant. object of this invention to provide a novel method and apparatus for displacing a core .barrel assembly through a drill string to the drilling location by fluid pressure imposed upon sealing structure such that the sealing structure will remain impervious at normal pressures and the core barrel assembly can therefore be located should it become hung up within .the.drillstring before reaching the drilling location. Another object is to novelly allow for passage of fluid through the sealing structure at abnormally high pressure, when the tube is stopped prematurely to provide for circulation of drilling fluid.

=One still further significant object of the present invention is the provision for novel structure and method for allowing fluid pressure to flow freely past the core barrel assembly during drilling and retraction thereof and prohibiting flow fluid past the core barrel assembly during advance thereof toward the leading end of a drill string at normal pressures and to permit passage of fluid with tube prematurely stopped at abnormally high pressures.

Another and no less important object of the present invention is to provide a novel coupling ridge structure on each of several companion resilient fingers comprising the trailing end of a core barrel assembly, which ridge structure securely couples the core barrel assembly to the outer tube at an internally-open groove and resists inadvertent uncoupling.

These and other objects and features of the present invention will become more fully apparent from the following description and appended clains, taken in conjunction with the accompanying drawings wherein:

FIGURE 1 is a fragmentary elevation shown partially in cross section of the presently preferred novel spearhead latching-outer tube coupling structure, disposed at the trailing end of a core barrel assembly (not shown), with the resilient fingers uncoupled from the outer tube of a drill string and the seal segments compressively closed upon each other to create a complete fluid seal;

FIGURE 2 is an elevational view similar to FIGURE 1 showing the ridge structure of the prongs or fingers operatively coupled into a recess in the outer tube of the drill string with the seal segments parted from each other to provide .a fluid passageway therebetween;

FIGURE 3 is a fragmentary elevation shown partly in cross'section illustrating the relation of the prongs and seal: segments when the prongs have been gathered by an overshot;

FIGURE 4 is a transverse cross section taken along lines 4'4 of FIGURE 1;

FIGURE 5 isa transverse cross lines 5.5 of FIG. 2;

.YFIGUREG is a perspective representationillustrating theiinterior of; one prong with a seal segment attached, of the-embodiment of theprevious figures;

FIGURE 7-is an end view of'one seal segment, whic is adapted 'to be appropriately disposed upon the interior 'angulari surfaces. of one-prong, the seal having a portion broken away to illustrate the hollow interior thereof; and FIGURE 8 is an elevation of the seal segment illustratedinFIGURE'J with a portion broken away to re- "veal the 'hollow interior thereof.

I Specific reference is now made to the drawings wherein: like numerals are usedto .identify like parts through- 0ut..=FIGURE-S 13 depict the outer tube coupling-spearhead latching structure 10 at the trailing end of a core section taken along a no further specific description of the remainder of the barrel assembly. Apart from the trailing end structure, I

the core barrel assembly may be substantially the same as that fully'described in my copending patent application Ser. No. 571,521, filed Aug. 10, 1966, and, therefore,

core barrel assembly in this specification is deemed necessary. The outer tube coupling-spearhead latching structure, comprising prongs 92, is illustrated as disposed within an outer tube 22 attached to the distal end of the drill pipe 23, which outer.tube is conventional except for an internally-open coupling recess 30 and another recess 32, each of which will be hereinafter more fully described. The presently preferred embodiment of the invention has greatest application where the drill string 23 and outer tube 22 are disposed in a horizontal or upwardly-directed drill hole, although it may be used in a downwardly-directed drill hole, for example, to obtain a pressure indication when the prongs have coupled to the outer tube.-

The spearhead latching-outer tube coupling structure Ill comprises a plurality of rigid prongs or bars, generally designated 92, which are preferably fabricated of tool steel and each is non-rotatably coupled to a leaf spring 94 interposed between the associated prong 92 and a core barrel assembly body disposed behind the swivel mechnism of the mentioned core barrel assembly (not shown). While four prongs or fingers 92 are illustrated in the figures, it should be appreciated that any suitable number of prongs could be utilized as desired. Together. each leaf spring and associated prong comprises a resilient radially-yieldable finger adapted to be displaced in a fish-tail, radial motion.

Each leaf spring 94 is biased radially outward and is non-rotatably connected to the associated prong at stem 118 such as by two or more rivets 116 (FIGURE 1). The rivets pass through apertures 117 of the stem 118 (FIGURE 6). The spearhead latching-outer tube coupling prongs 92, in the illustrated embodiment, are all of identical construction, material and dimensions. The prongs are constructed and arranged in an array so that a generally hollow space is provided central of the prongs, to allow for the mentioned fish-tail, radial motion. Significantly, it should be noted that the prongs have no interrelated mechanical parts which must move relative to each other during coupling and uncoupling of the core barrel assembly with the outer tube 22. It should also 3e kept in mind that the prongs 92 serve a three-fold purpose; namely, (1) to selectively accommodate coupling of the core barrel assembly with the outer tube, (2) to accommodate spearhead latching of an overshot and outer tube uncoupling for retrieval of the core barrel assembly from the drill hole and (3) to accommodate holding of the overshot latching and outer coupling structure of each prong away from the interior wall of the drill string as the core barrel assembly is propelled to the drilling site.

Structurally, in transverse cross section, each prong 92 as shown in FIGURES 4 and 5, has a wedge-shaped back or inside surface and an arcuate surface disposed at the -'front or exterior. As best illustrated in FIGURE 1 and 2.

each prong comprises aski or cam which accomplishes purpose (3), above, and, therefore, tends to prevent'hanging up of the core barrel assembly within the drill string, such as on a poor tolerance lip at a threaded drill string joint.

Each cam 130 also prevents wear on the adjacent .coupling ridge 132 which is separated from the cam 130 in the illustrated embodiment by an arcuate groove 134, each disposed at the exterior surface of each prong 92. In the drilling position, as illustrated in FIGURE 2, each cam 130 on each of the four illustratedprongs 92 is disposed within the annular recess 32 previously mentioned. This disposition accommodates close and secure coupling of each ridge-132 within the two-way coupling annular'recess 30. The annular recess 30 is'convergently tapered toward the center of the outer tube 22 providing opposed locking abutment surfaces 133'and 135 at the upper and lower edges of groove 30.

Each coupling ridge 132 couples directly with the outer tube and comprises an outer arcuate mating surface 136, an upper tapered coupling surface 138 adapted to be disposed adjacent the surface 133 and a lower tapered coupling surface 140 adapted to be disposed adjacent the surface 135. See FIGURES 2 and 6. Each coupling ridge 132, at surfaces 138 and 140, is tapered divergently outward in a configuration complementary to the configuration of the recess 30. Thus, as illustrated best in FIGURE 2, the upper coupling surface 138 achieves fail-safe coupling with upper surface 133 of the recess against inadvertent rearward release during drilling regardless of whether the drilling is with or counter to the force of gravity. The lower coupling surface 140 of the ridge 132 provides fail-safe coupling against forward release of the core barrel assembly in the direction of the bit.

The distal end of each prong 92 comprises a spearhead hook 146 having an exterior tapered though arcuate surface 148 and an overshot latching shoulder 150. The shoulder 15% is separated from the adjacent coupling ridge 132 by an arcuate groove 152 disposed in each prong. Inspection of FIGURES 1 and 2 shows that, during displacement to and from the drilling site as well as during drilling, the transverse position of each spearhead hook 146 is spaced from the inner wall of the outer tube 22.

The tapered surface 148 of each prong 92 accommodates inward radial gathering or clustering of the prongs when an overshot (not shown) is brought in contact with the tapered surface 148 of each prong during advance of the overshot through the drill string toward the bit. The inward gathering of the prongs toward the radial center line of the outer tube accommodates further displacement of the overshot along the tapered surface 148 of each prong thereby first radially uncoupling the coupling ridge 132 from the annular recess 30, and thereafter latching the overshot upon the shoulder 150 of each prong. The core barrel assembly may then be removed from the drill string with the overshot.

See the mentioned US. patent application Ser. No. 571,521, for a more detailed explanation concerning the foregoing.

Each prong 92 presents on the back or inside surfaces 169 thereof adjacent the cam 130, an essentially V-shaped seal segment 170. Each seal segment 170 comprises angularly related legs 172 and 174 which are preferably molded directly to the inside surfaces 169 of the associated prong adjacent and essentially coextensive with the annular portion of the ski 130. The surfaces 169 at which molding takes place are preferably roughened or grooved to improved the bond. Alternatively, each seal segment might be epoxy bonded or otherwise adhesively secured in the described position. In the illustrated embodiment, the legs 172 and 174 are disposed at right angles relative to one another and a fillet 176 exists at the inside vertex of the seal segment 170 between the legs. Thus, the internal configuration of the seal segment 170 at the bonded faces thereof is complementary to the adjacent inside surfaces 169 of the prong 92, the fillet 176 being disposed within the axial groove 171 in each prong 92.

Each seal segment 170 is preferably formed of neoprene although other suitable resilient materials with memory could be used. Each leg 172 and 174 is interiorly hollow at 180 and 178, respectively, the hollow portions comprising vertically-elongated apertures which join each other and respectively open to the exterior at the extreme ends of the legs 172 and 174. See especially FIGURES 7 and 8. The hollow apertures 178 and 180 accommodate substantial compression or flattening deformation of each seal segment 170 (FIGURE 3) when the prongs 92 are gathered or clustered by the advancing overshot. The advantage of such compression will be hereinafter more fully described.

In the presently preferred mode of operation of the illustrated embodiment, the latch structure 10 assumes the general position of FIGURE 1 after it is placed within the drill string and as the core barrel assembly (not shown) including the latch structure 10 is dis laced toward the coupling or drilling site at the leading end of the outer tube 22 up to the time the coupling ridge 136 seats into the annular recess 30.

In the position of FIGURE 1, each prong 92 is situated somewhat toward the axial center line of the outer tube 22 so that each seal segment 170 will be disposed in compressive contiguous relation with two adjacent seal segments, as illustrated in FIGURES 1 and 4. In this position the seal segments 170 cooperate to form a seal at the trailing end of the core barrel assembly to preclude the flow of drilling fluid axially by the latch structure 10, the contiguous relation of the arcuate portion of each ski with the interior surface of the drill string assisting in establishing the mentioned fluid seal.

Thus, the pressure of the drilling fluid at the trailing end of the latch structure 10 will exert an axially-directed force upon the closed seal segments 170 and the top surface of the cams 130 to propel the core barrel assembly to the leading or drilling end of the drill string, without reliance upon any other structure.

Should the latch structure 10 or related core barrel assembly become hung up within the drill string, the fluid seal is nevertheless maintained until abnormal high pressures occur indicating stoppage. Pressure measuring techniques plus fluid volume and time measurements can be used to locate such a stopped core barrel assembly. Abnormally high pressures cause the resilient seal segments to distort sutficiently to pass fluid. This passage of fluid is valuable in an urgent hole condition, to prevent stuck pipe.

When the core barrel assembly reaches the drilling or operating position at the leading end of the outer tube 22 and just before the latch structure 10 couples in the drilling position, the position of FIGURE 1 will prevail. Then each cam 130 and adjacent coupling ridge 132 will be essentially simultaneously laterally displaced by the outward bias of springs 94 into annular recess 32 and annular coupling recess 30 respectively, thereby obtaining the position illustrated in FIGURES 2 and 5.

As best shown in FIGURES 2 and 5, the seal segments 170 part or separate from each other as each prong 92 is laterally displaced so that an axial passageway 190, cross-shaped in cross section, is formed adjacent the seal segments 170. The axial passageway 190 provides for downward circulation of drilling fluid past the latch structure and by the core barrel assembly, which drilling fluid is conventionally used to cool the bit during drilling.

When it is desired to remove the core barrel assembly from the coupled relation with the outer tube 22, as illustrated in FIGURE 2, an overshot (not shown) is advanced over the spearhead hook 146 and latching shoulder as previously described. The overshot gathers or clusters the prongs 92 to laterally displace the coupling ridge 132 and cam 130 out of the respective recesses 30 and 32 toward the axial center line of the outer tube 22. Each seal is thereby compressed or deformed to a substantially flattened condition as best illustrated in FIG- URE 3. In this position, a fluid passageway exists between the cams 130 and the interior surface of the outer tube 22 so that the core barrel assembly may be completely removed by the latched overshot from the drill string in a rapid manner without simultaneously swabbing the hole dry of drilling fluid.

The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiment is, therefore, to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the mean- 7 ing and range of equivalency of the claims are therefore to be embraced therein.

What is claimed and desired to be secured by United States Letters Patent is:

1. Structure at the trailing end of a core-accepting and core-retrieving apparatus adapted to be displaced under pressure of drilling fluid through a string of drill pipe and into coupled relation with an interior recess in an outer tube adjacent the drilling site, said structure comprising a plurality of spaced fingers independently radially yieldable through a fish-tail motion, each finger joined at the leading end thereofto the remainder of the apparatus and each finger presenting a free trailing end, each finger also being biased generally radially outward and having means adapted to couple with said outer tube recess,

said structure further comprising the improvement of fluid seal means comprising surface portions of said fingers which continuously frictionally engage the interior surface of the drill pipe under force of said bias during said displacement and compressible segments interposed between the fingers, each segment being integrally joined to one finger, the compressible segments presenting opposed surfaces that (a) compressively close one upon another during the said displacement to, in conjunction with said surface portions, completely seal the drill pipe so long as the pressure of the fluid is within a predetermined range and (b) part one from another to accommodate fluid flow across the fluid seal means when said coupled relation is achieved.

2. A core barrel assembly, adapted to be latched in a recess in an outer tube of a drill string during drilling, comprising outer tube coupling-spearhead latching means comprising a plurality of essentially radially yieldable means carried at the trailing end of the core barrel assembly, said radially yieldable means being cantilever-supported for fish-tail movement and normally disposed in a position generally parallel to the longitudinal axis of the core barrel assembly and biased outwardly at spaced radial locations, said radially yieldable means comprising (a) coupling means adapted to be disposed in said recess by said outward bias to accommodate drilling, (b) spearhead means adapted to be latched with overshot means through essentially radial displacement of the radially yieldable means out of coupling disposition with the recess means counter to said outward bias to accommodate removal of the core barrel assembly from the outer tube and (c) resilient compressible seal means inwardly presented by a portion of each radially yieldable means when the radially yieldable means are disposed within the drill string out of coupled relation with the recess means and out of latched relation with overshot means.

3. In a core barrel' assembly, a plurality of prong means comprising the trailing end of the core barrel assembly, said prong means being disposed in spaced relation one to another in a generally concentricarray about the longitudinal axis of the core barrel assembly and essentially radially biased outward but accommodating essentially inward radial displacement counter to said bias into hollow space means between the prong means, which prong means comprise (a) means disposed at the distal end for latching with overshot means following inward radial displacement of the prong means to accommodate removal of the core barrel assembly from a drill hole, (b) means adjacent said overshot latching means to couple with recess means disposed within a drill string outer tube responsive to said outward bias during drilling operation, (c) means adjacent the recess coupling means for contacting the interior surface of the drill string outer tube thereby urging the prong means inwardly counter to the bias when the core barrel assembly is displaced within the drill string and (d) resiliently deformable means adhered to the prong means adjacent the hollow space means at a location, essentially opposite the contacting means whereby the hollow space means is substantially occluded by the deformable means and axialfluid flow through the core barrel assembly is precluded only when the prong means are inwardly radially displaced by said urging action counter to the outward bias.

4. In 'a method of positioning a core barrel assembly having a cantilevered array of trailing toothed prongs in drilling position within an open coupling groove in an outer tube of a drill string, the steps of: depositing the core barrel assembly within the hollow of the drill string, gathering prong-connected seal structure to a compressed state adjacent the longitudinal axis of the core barrel to form a fluid seal while biasing each said cantilevered prong essentially arcuatelyoutward in a generally radial directioninto contiguous relation with the inside surface of the drill string, propelling the core barrel assembly along the drill string toward the leading end thereof while retaining each contiguous relation by developing .a pressure head adjacent the trailing end of the core barrel assembly, disposing a tooth of each prong radially adjacent said coupling groove, displacing said cantilevered prong essentially arcuately outward in a generally radial direction responsive to said bias to dispose each said tooth within said coupling groove, and releasing the seal structure from the compressed state as the prong are outwardly displaced to open at least one passageway at the seal structure and accommodate fluid communication by the core barrel assembly while each prong tooth is so disposed within the coupling groove.

v 5. A method as defined in claim 4 further comprising the'steps of: locating an overshot adjacent the trailing end of the core barrel assembly, displacing the overshot toward the leading end of the drill string to exert a forward force on the trailing end of the toothed prongs to displace each tooth out of the coupling groove, tightly gathering and displacing the seal structure out of the open position into a highly compressed state thereby closing said passageway, latching said overshot with the yieldable prongs so as to hold the prongs inward of the interior surface of the drill string to allow fluid flow therebetween and subsequently, retracting the overshot and latched core barrel assembly from the drill string.

6, In a core barrel assembly adapted to be latched in an outer tube of a drill stringduring drilling, a plurality of prong means comprising the trailing endof the core barrel assemblyhiasedradially outward but accommodating radially inward displacement counter to said bias, the prong'means being cantilever-mounted in a spaced, generally concentric array around the. axis of the core barrel and each prong means comprising (a) spearhead means adapted to be selectively latched with an overshot means and (b) coupling means comprising an outwardly-directed tooth having" opposed top and bottom faces divergently radially tapered in an outward direction, said tooth adapted recess when th'e 'prong means are radially inwardly and outwardly displaced.

"7. core'bar'rel 'a ss emblyifor disposition in a recess in an outentube'of a drill string comprising a plurality of spaced, outwardly biased prongs comprising the trailing end of the core barrel assembly, said prongs each comprising spearhead latching structure, radially extending first ridge structure sized and shaped to couple with the recess in the outer tube and radially extending second ridge structure adapted'to be disposed in a second recess in the outer tube and a resilient, yieldable seal secured to each prong adjacent the second ridge structure,each seal presenting angularly related faces forming an apex at the intersection thereof, which apex is inwardly directed and situated in a space between the prongs, the seal on each prong adapted to (a) complementarily engage adjacent seals to preclude fluid flow therethrough when disposed within the drill string, through not coupled to the outer tube, (b) separate from each adjacent seal to provide an axial fluid passageway through the core barrel assembly only when the first ridge structure is coupled within the recess in the outer tube and (c) compress to accommodate inward gathering of the prongs as an overshot advances over the spearhead latching structure.

8. An assembly as defined in claim 7 wherein said seals are interiorly hollow to facilitate compression thereof when the prongs are inwardly gathered by the advancing overshot and to accommodate fluid flow therethrough when deformed by fluid pressure exceeding a predetermined value.

9. In a core barrel assembly, the improvement comprising resilient compressible seal structure disposed between and fastened to yieldable fingers at the trailing end of the assembly defining at least one axial fluid passage through the seal structure when the seal structure is essentially free of transverse compression, the passage being closed to fluid flow by an inwardly transverse gathering of the fingers to place the seal structure under transverse compression.

10. A core barrel assembly of the type defined in claim 9 wherein said seal structure comprises elastorneric material and is bonded to the fingers.

References Cited UNITED STATES PATENTS 1,716,092 6/1929 Smith 175-246 1,830,012 11/1931 Barrett et al. 175-246 2,046,798 7/1936 Thrift 175246 X 2,145,170 1/1939 Frenzel 175--236 X 2,352,612 7/1944 Boynton 166-125 2,857,138 10/1958 Svendsen et a1. 175246 X CHARLES E. OCONNELL, Primary Examiner IAN A. CALVERT, Assistant Examiner US. Cl. X.R. 175-236, 243, 246 

